The invention relates to weft insertion apparatus for shuttle-type weaving looms, and more particularly to arrangements for hydraulically actuating a cylinder-mounted piston coupled to the shuttle, with a forward motion of the piston from a rearmost position within its cylinder being effective to initiate a launch of the shuttle.
In known weft insertion facilities of this type, hydraulic fluid is introduced into the cylinder on both sides of the piston, with an excess hydraulic pressure being imposed on the rear side of the piston when the forward stroke thereof is to be initiated, and with an excess pressure being introduced on the forward side of the piston when the return stroke is to be effected. Such arrangement suffers from the disadvantage that the weight and resistance of the hydraulic fluid on the end of the piston opposed to the end at which the excess pressure is applied is considerable, and in fact is often greater than the load represented by the shuttle itself. Consequently, the launching arrangement must be of bulky and expensive heavy-duty construction.
In addition, in known arrangements of this type the cylinder in which the shuttle-launching piston is situated is mounted on a rotary underslay of the loom, while the reservoir for hydraulic fluid to be periodically introduced on both sides of the piston for the above-mentioned purposes is disposed on a fixed portion of the loom frame. Consequently, the conduits that transfer fluid from the reservoir to the cylinders must be of flexible and resilient construction in order to accommodate the relative motion of these parts, thereby adding to the complexity and expense of the unit. Moreover, the relative fragility of such flexible conduits, together with the fact that the movement of the piston exerts a tremendous compressive force on the hydraulic fluid disposed on the then-downstream portion of the piston, renders the facilities susceptible to severe hydraulic leakage problems.